1. Field of the Invention
The present invention relates to the testing of network devices such as integrated network switches configured for switching data packets between subnetworks.
2. Background Art
Local area networks use a network cable or other media to link stations on the network. Each local area network architecture uses a media access control (MAC) enabling network interface devices at each network node to access the network medium.
Switched local area networks such as Ethernet (IEEE 802.3) based systems are encountering increasing demands for higher speed connectivity, more flexible switching performance, and the ability to accommodate more complex network architectures. For example, commonly-assigned U.S. Pat. No. 5,953,335 discloses a network switch configured for switching layer 2 type Ethernet (IEEE 802.3) data packets between different network nodes. Hence, network switch designers and test engineers need to be able to minimize the time and expense needed to evaluate designs during prototyping of Ethernet-based network systems.
One problem associated with testing network-based switch chips involves the limited availability of the sample chips for testing hardware associated with interaction between multiple chips. For example, the network switch disclosed in U.S. Pat. No. 5,953,335 describes an expansion port that may be used for interconnecting multiple network switch chips for transfer of packet data according to a prescribed bus protocol, such as peripheral component interconnect (PCI) bus protocol. However, use of the expansion port assumes the availability of at least one additional network switch chip for interconnection of the expansion ports of the respective network switch chips.
Hence, there is a concern that the expansion port and associated operations cannot be tested or validated if only one network switch chip is available for testing. In addition, even if a second network switch chip was available for testing of the expansion ports, a detected error between the expansion port operations creates the additional problem of determining whether the detected error is due to a problem in the first switch chip under test, a problem in the second switch chip used for testing the expansion port of first switch chip, a problem in the connection between the two expansion ports, or any combination of the foregoing.